96 LX Civic has CEL code 67
Is there a way I can test the Cat and o2 sensors to see which is bad? CARB cats are hella expensive & I dont want to replace that if it's just an o2.

 

Oh and after I reset the CEL it takes a couple days or more to come back on, occassionally the car stumbles on acceleration when cold while throwing the CEL.

 

I say O2 sensor. It's not often cats go bad. You can test the O2 but you need a multimeter.

 

I had a bad cat and my nox was off the charts when I went to go get it smog-ed for cali emissions. A new o2 sensor is not that expensive and I would replace that before replacing the cat. Plus you are suppose to replace those so often anyways as part of a tune up. Like the previous op said, you can test the o2 with a volt meter. You can buy one pretty cheap at any store, its a good investment.

 

Yeah actually I had a multimeter but it no longer works, was thinking about picking a new one up monday.
What would I be measuring for on the sensor, resistance?

 

Yes you will be measuring the resistance. According to the helms manual, you need to warm the car up to operating temperature, then open the throttle wide open then close it. Then you need to measure the voltage between the conductor terminal and the body ground. The voltage should be above .5v during wide open acceleration? is voltage below .4v during closed throttle deceleration from 5000 rpm. If no replace o2 sensor.

 

Couldn't you pull the O2 sensor before the cat and drive it? If it drives better, you have a clogged cat. I would just go buy a new O2 sensor they're pretty cheap.

 

How many miles are on the car? I would just replace the cat and o2 sensor.

But then again you live in cali, so you can't just buy any cat lol

 

if it was the O2 sensor, wouldn't you get the "1" or "2" code along with the "67"? guy at my muffler shop said a bad cat would cause the plugs to foul out. anybody ever hear of that? i don't think he's tryin to screw me. he quoted me $250 for a cat replacement which i didn't think was too bad.

 

A bad O2 sensor will NOT throw code 67/P0420. This code is almost always caused by a bad catalytic converter, though an exhaust leak should first be ruled out.

 

0bd2 civics have codes specific to the cat.

On a trip back home from Hilton Head, I got a code that essentially told me straight up my cat converter died. If your car tells you it's the o2, it's the o2.

EDIT: Thanks Ron. This is the specific code I through.

 

so i used this forums "THE Check Engine Light (CEL) THREAD" which was pretty cool btw, and got the bad cat code, 67. should i follow this up with a trip to autozone for a more detailed obs2 diagnostic? thanks for the replies. nice to finally find a forum that actually has responses.

 

^Yes, because there can be different answers.

I had gotten it before it finally died with a diagnostics check that read "low threshold," which basically means it was on it's way out.

 

Let me try to explain...

The car has two o2 sensors on it, one for A/F and one just to check on the cat. The a/f one is before the cat and the one for the cat is either on the cat or behind it.

The cat one can show a viable voltage however the voltage is not correct in relationship to the cat. The computer see's a good voltage from the O2 sensor so it doesn't throw a code for the O2 sensor. However that voltage signals the computer that the cat is below threshold.

I would give it a 95% chance that it is the O2 sensor.

 

Ron would beg to differ.

 

1 important detail i left out. the car has 188,000 miles on it. how long do cats usually last? an who's ron?

 

My car is at 130xxx. And RonJ is the smartest man you'll ever meet over the internet.

 

sorry, the quotes threw me off. i thot you had ron arguing with himself for a sec there. :D

 

cat

 

http://cgi.ebay.com/ebaymotors/ws/eB...tchlink:top:en

since i live in a state that doesn't have an inspection code, will i still pull a 67 with somethin like this?

 

Yes, this.

At one point, I had 4 different OBD2 cars in my family all throwing the 0420 code at once. It's the official 'bad cat' code. It basically means that your second O2 is not reading enough of a difference in emissions from your primary O2.

As someone mentioned before, you can remove the secondary O2 and put it somewhere that it would register clean air. The code should go away after a few drive cycles, thus verifying it's a bad cat. If the code doesn't go away, then there is something wrong with the secondary O2 or the wiring.

So, theoretically the code could be caused by a problem with the secondary O2 sensor, but while I'm sure that happens, I've never seen an 0420 NOT be a bad cat.